what upgrade options for a 2lts. "S"

[targa6911s]

What are the usual upgrades (if any) for a 2lts. "S" engine (1969) ?

[StuttgartDavid]

I have a '68 2.0 S, which can be upgraded with bigger carb venturies, colder plugs and a sport muffler (all detailed in the factory sport tuning manual) to go from 160 hp to 175-180hp, but with a loss of low end due to the bigger venturies.

You, my friend have fewer upgrade possibilities, BECAUSE THE FACTORY ALREADY DID ALL THE UPGRADING FOR YOU! There is simply no way to get more power out of that engine without major reengineering, other than adding a twin pipe sport muffler, which is worth 5-10hp.

You may get some marginal benefit from a crankfire ignition system or well made and tuned headers, but there are simply no major areas of gain that the factoy didn't already optimize with the S engine.

The next step is to go with twin plugs and 906 cams like the 210-220hp factory race motors. This will require reworking the heads and MFI, and will kill all power below 5000rpm. From 5-8000rpm it will scream, until it blows up in 50 to 100 hours.

The only practical way to upgrade that engine's potential is with a close-ratio, limited slip gearbox that reduces rpm drop after shifts and keeps you well into the powerband. With that and uprated suspension, tires, and basic safety mods, you will have what is still one of the fastest street cars ever sold.

Bottom line: focus on learning to drive it to the edge of its performance envelope, not on making the already large envelope larger.

[Jack Olsen]

Do a search on "Airport Gears." Also see my thread on my tranny.

You've got a great engine there, in a car with phenomenal handling characteristics. If muscle is your goal, I'd say trade it for a Turbo.

[jluetjen]

The obvious choice is 84mm or 85mm 2.2S p+c's (9.4:1 CR, ~175 HP) or 2.7 p+c's (90mm) which will result in a 2.5 (6.5:1 CR, ~190 HP???). Curt on this BBS has a 2.5 which he loves and I'm sure that he'll chime in about it. By the way, when you do either you will lose a little bit of compression ratio from the quoted for the pistons because the 2.0 combustion chambers are little bigger then the later 2.2/2.4/2.7 heads. If you go with the 2.5 option, you might want to consider going with some Mahle aftermarket pistons as they have been advertising lately in the 9.5:1 version. With the short stroke and large chambers, you might wind up with about a 7.5:1 CR. You can also look at JE pistons which are available in the 90mm size with a 10.5:1 CR. This will result in about an 8.5:1 CR once installed in your engine. Any of these will require having the MFI updated to take into account the extra capacity or a conversion to Webers. I believe that you will also need to have your heads machined to accept the larger bore and later style head gaskets.

Other then that you move past "bolt-on" and you'll be talking about building a race motor, 10.5:1 CR p+c's, Hotter cams and other things which will require further changes to support higher rev's. The good news is that your "S" heads have fairly large valves and ports, so you will not be limited there like a T/E owner would be. You should be able to do a lot before you need to port the heads further.

BTW: I believe that 2.0 S heads are fairly rare. If you are going to machine the heads, you might want to consider selling the heads (or in fact the whole motor) to a vintage racer and turn around and buy later (2.2/2.4/2.7) heads/motor and have them ported. It might be cheaper in the end.

[cegerer]

I do like my 2.5 setup, partly because it is a 'period correct' modification. There is no logic to that, of course. Dropping a big 3.2 or 3.6 in would provide greater horsepower - and it may be cheaper too!! I do think the high-comp 90mm/92mm pistons would be fantastic in your S motor - "there's no replacement for displacement" .

But I really like the idea of re-gearing. While not cheap, it does allow one to get maximum efficiency out of a motor (i.e. why have a 140MPH+ top speed capability if you never go over 120MPH?). The long-range plans for my car include 'airport gearing', along with many, many other motor modifications I've gathered from this BBS. And thanks to John's numerous explanations of the importance of port sizes, that will be a key component in any future rebuild of my motor! -- Curt

[pwd72s]

I'd think long and hard before deciding to do the machining needed for a bigger bore on an original 911S case. I know more than one guy who did that to a 2.4S, to go to 2.7, now wishing they'd just bought a replacement case & built the engine...my two cents.